package com.lxf.clouduser.utils;

/**
 * @author 罗兴发
 * @data 2025/6/16 15:13
 * @description：雪花算法-实现群号唯一性
 */
public class SnowflakeIdGenerator {
    // 开始时间戳 (2023-01-01)
    private final long twepoch = 1672502400000L;

    // 机器ID所占的位数
    private final long workerIdBits = 5L;
    // 数据标识ID所占的位数
    private final long datacenterIdBits = 5L;
    // 支持的最大机器ID，结果是31 (这个值在位运算中不会溢出)
    private final long maxWorkerId = -1L ^ (-1L << workerIdBits);
    // 支持的最大数据标识ID，结果是31
    private final long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);
    // 序列号在ID中所占的位数
    private final long sequenceBits = 12L;

    // 机器ID需要左移的位数，12
    private final long workerIdShift = sequenceBits;
    // 数据标识ID需要左移的位数，17
    private final long datacenterIdShift = sequenceBits + workerIdBits;
    // 时间戳需要左移的位数，22
    private final long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;

    // 生成序列的掩码，这里为4095 (0b111111111111=4095)
    private final long sequenceMask = -1L ^ (-1L << sequenceBits);

    // 工作机器ID(0~31)
    private long workerId;
    // 数据中心ID(0~31)
    private long datacenterId;
    // 毫秒内序列(0~4095)
    private long sequence = 0L;
    // 上次生成ID的时间戳
    private long lastTimestamp = -1L;

    public SnowflakeIdGenerator(long workerId, long datacenterId) {
        if (workerId > maxWorkerId || workerId < 0) {
            throw new IllegalArgumentException(String.format("worker Id can't be greater than %d or less than 0", maxWorkerId));
        }
        if (datacenterId > maxDatacenterId || datacenterId < 0) {
            throw new IllegalArgumentException(String.format("datacenter Id can't be greater than %d or less than 0", maxDatacenterId));
        }
        this.workerId = workerId;
        this.datacenterId = datacenterId;
    }

    /**
     * 产生下一个ID
     */
    public synchronized long nextId() {
        long timestamp = timeGen();

        // 如果当前时间小于上次ID生成的时间戳，说明系统时钟回退过这个时候应当抛出异常
        if (timestamp < lastTimestamp) {
            throw new RuntimeException(String.format("Clock moved backwards. Refusing to generate id for %d milliseconds", lastTimestamp - timestamp));
        }

        // 如果是同一时间生成的，则进行毫秒内序列
        if (lastTimestamp == timestamp) {
            sequence = (sequence + 1) & sequenceMask;
            // 毫秒内序列溢出
            if (sequence == 0) {
                // 阻塞到下一毫秒,获得新的时间戳
                timestamp = tilNextMillis(lastTimestamp);
            }
        } else {
            // 时间戳改变，毫秒内序列重置
            sequence = 0L;
        }

        // 上次生成ID的时间截
        lastTimestamp = timestamp;

        // 移位并通过或运算拼到一起组成64位的ID
        return ((timestamp - twepoch) << timestampLeftShift)
                | (datacenterId << datacenterIdShift)
                | (workerId << workerIdShift)
                | sequence;
    }

    protected long tilNextMillis(long lastTimestamp) {
        long timestamp = timeGen();
        while (timestamp <= lastTimestamp) {
            timestamp = timeGen();
        }
        return timestamp;
    }

    protected long timeGen() {
        return System.currentTimeMillis();
    }

    private String getIds(long l){
        String s1 = String.valueOf(l);
        String s3 = s1.substring(9, 10);
        String s4 = s1.substring(17);
        if (Integer.valueOf(s3)==0||Integer.valueOf(s4)==0){
            return getIds(l);
        }else {
            String s5 = s1.substring(9);
            System.out.println("完整群号为："+s5);
            return s5;
        }
    }

    /**
     * 获取最终唯一群组号
     * @return
     */
    public String getGroupId(){
        SnowflakeIdGenerator s = new SnowflakeIdGenerator(1,1);
        long l = s.nextId();
        String groupId = s.getIds(l);
        return groupId;
    }
}
